1. Field of the Invention
The present invention relates to a surveillance camera capable of adjusting a position thereof and a method of controlling the same. More particularly, the present invention relates to a surveillance camera capable of correctly adjusting its position by adaptively initializing positions of a pan motor and a tilt motor while they are being driven, and a method of controlling the same.
2. Description of the Related Art
A speed dome camera, an example of a closed-circuit television (CCTV) monitoring system, moves transversely and perpendicularly by pan and tilt functions and detects any movement within a monitored area. The speed dome camera is generally mounted in a hemisphere or sphere shaped housing.
The pan function is for transversely panning a camera by a pan motor through a substantially 360-degree range, and a tilt function is for perpendicularly panning the camera by a tilt motor through a substantially 90-degree range. The monitored area is expandable by the pan and tilt functions.
A stepping motor capable of varying a speed thereof is used as the pan motor and the tilt motor. A rotating direction and a speed can be adjusted in accordance with a step, that is, a driving pulse, output from a controller of the dome camera.
The dome camera is provided with a pan sensor and a tilt sensor for position initialization of the pan motor and the tilt motor. When the dome camera is turned on, the pan motor moves from a current position to a pan sensor position, and the tilt motor moves from a current position to a tilt sensor position in a certain direction, thereby initializing a counter of the driving pulse. That is, the counter is initialized after the dome camera is on. This is because positions of the pan motor and the tilt motor are determined according to the counter of the driving pulse, thereby driving the dome camera adaptively.
FIG. 1 shows a pan motor 10 of a dome camera rotating clockwise (CW) or counterclockwise (CCW) through a substantially 360-degree range. When a standard position detected by a pan sensor 12 corresponds to a current position P1, with the dome camera turned on, the pan motor 10 moves so that the standard position thereof is detected by the pan sensor 12.
When the standard position of the pan motor 10 is detected by the pan sensor 12, and the counter of the driving pulse is initialized, the pan motor 10 rotates back until the standard position thereof corresponds to the current position P1 and performs a monitoring function, rotating CW or CCW according to the output driving pulse. The dome camera detects the position of the pan motor 10 as rotated, based on a value of the counter of the driving pulse, and outputs a driving pulse for moving to a next position P2.
For example, assuming that the driving pulse required for the standard position of the pan motor 10 to move from the current position P1 to the next position P2 is 90 after the initialization of the driving pulse counter, the dome camera outputs 90 as the driving pulse to the pan motor 10. Therefore, if the driving pulse counter is 90, the dome camera determines the standard position of the pan motor 10 to correspond to the next position P2 and outputs a driving pulse for moving to another next position P3. The position initialization and the output of the driving pulse of the pan motor 10 are applied in almost the same manner in the tilt motor and are not separately illustrated.
However, since the conventional camera applies the stepping motor, operated in accordance with the driving pulse, for the pan motor 10 and the tilt motor, loss of the driving pulse occurs when operating the pan motor 10 and the tilt motor. The loss is induced when changing the speed or the rotating direction of the pan motor 10 and/or the tilt motor. As the numbers of losses are accumulated, the pan motor 10 and/or the tilt motor would fail to correctly move to desired positions corresponding to the output driving pulse.
In other words, the conventional dome camera initializes only the driving pulse counter of the pan motor 10 and the tilt motor, but does not reinitialize the positions of the pan motor 10 and the tilt motor although the error caused by the loss of the driving pulse is accumulated. Therefore, the pan motor 10 and the tilt motor cannot be correctly placed within the monitored area, and accordingly, photographing or video capture of the monitored area where monitoring is required by a user cannot be completely, consistently or accurately performed.